1. Field of the Invention
The present invention relates to a rotary compressor including, in a sealed vessel, a driving element and a rotary compression element driven by a rotary shaft of this driving element.
2. Description of the Related Art
Heretofore, a rotary compressor such as a multistage compression type rotary compressor including first and second rotary compression elements includes, in a sealed vessel, a driving element and the first and second rotary compression elements driven by a rotary shaft of this driving element.
The first and second rotary compression elements include an intermediate partition plate; upper and lower cylinders disposed on and under this intermediate partition plate; rollers which are fitted into eccentric portions disposed on a rotary shaft with a phase difference of 180 degrees to eccentrically rotate in these cylinders; vanes which abut on the rollers to define the insides of the cylinders into low pressure chamber sides and high pressure chamber sides, respectively; an upper support member and a lower support member which block an upper opening surface of the upper cylinder and a lower opening surface of the lower cylinder and which have bearings of the rotary shaft, respectively; and upper and lower discharge muffling chambers. Each discharge muffling chamber is connected to the high pressure chamber side in each cylinder by a discharge port. In each discharge muffling chamber, a discharge valve is disposed which openably blocks the discharge port. An O-ring is attached to the surface of the lower support member on which the bearing and the blocking plate abut, and the discharge muffling chamber formed in an outer periphery of the bearing is sealed with the ring (see, e.g., Japanese Patent Application Laid-Open No. 2003-97473).
Here, each discharge muffling chamber is sealed with the O-ring between the bearing and the blocking plate as described above, but heretofore refrigerant leakage is generated from the surface on which the bearing and the blocking plate abut, and improvement of a sealing property of the discharge muffling chamber has been demanded.
Especially in a high inner pressure type multistage compression rotary compressor including the sealed vessel having a high pressure, there is a large pressure difference between the discharge muffling chamber of the first rotary compression element having an intermediate pressure and the sealed vessel having a high pressure. Since there is such a pressure difference, the sealing property of the discharge muffling chamber cannot be secured by disposing the conventional O-ring only, and deterioration of a volume efficiency is incurred.
In a case where an O-ring having a sealing width larger than that of the conventional O-ring is attached to the bearing in order to improve such a sealing property of the discharge muffling chamber, a thickness dimension of the bearing on an outer diameter side of an O-ring groove decreases owing to enlargement of the O-ring groove. Especially, as to the bearing having the discharge valve on an outer peripheral surface thereof, the outer peripheral surface of the bearing is formed into a shape cut by the discharge valve. Therefore, when the O-ring groove enlarges, it is not possible to secure the thickness of the bearing on the side of the outer diameter of the O-ring in the vicinity of the discharge valve.
Moreover, in a case where an concave portion is formed in the whole periphery of a bearing portion to constitute the discharge muffling chamber, deformation of a seal portion is caused owing to shortage of strength of the bearing portion, and the sealing property is deteriorated.
On the other hand, in a case where the diameter of the bearing is enlarged in order to enlarge the O-ring groove and increase the strength of the bearing, the discharge muffling chamber formed in the outer periphery of the bearing is reduced, and an effect of muffling a refrigerant discharged from the cylinder is reduced. Moreover, a position of the discharge port needs to be changed, and the deterioration of the volume efficiency is also caused.